Having a quick look at the ‘Built-in Drawing Title’ object, it appears that the drawing dimensions are stored in a parameter called ‘AC_DrawingRect’.
In particular …
xo = AC_DrawingRect: yo = AC_DrawingRect
x1 = AC_DrawingRect: y1 = AC_DrawingRect
Or if you want to use the layout width then it is the ‘AC_LayoutRect’ parameter.
Versions 6.5 to 22
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision M6800 - i7 4700MQ @ 2.40GHz, 16GB RAM, AMD FirePro M6100 (2GB), Windows 7 64bit